It is well known that, during the smoking of a cigarette, the quantity of flavour components in the smoke tends to increase as the cigarette is smoked, so that the last puff usually contains approximately three times the amount of flavour components than the first puff.
Attempts have been made to provide cigarettes in which the tobacco blend in the filler rod is varied to achieve a more uniform taste to the tobacco smoke as it is smoked. Recently there was introduced to the market in the Federal Republic of Germany under the brand name "DOUBLE BLEND", a cigarette having a rod composed of two different blends. The lighting end of the cigarette contains a blend of strong aromatic tobaccos while the filter end of the cigarette consists of lighter, milder tobaccos, to provide a more even taste than a single one of the blends or a single blend make up of the two types of tobacco. It is claimed for this cigarette by the manufacturers that not only is a strong even tasting cigarette provided but this result is achieved with low tar and nicotine values of 8 mg and 0.8 respectively.
One of the major problems associated with such two-blend cigarettes is production of a continuous filler rod at the high speeds, typically up to about 4000 cigarettes per minute, required in modern production. Information currently available from trade literature (Tobacco Journal International, Jan. 1987) indicates that the individual blends are fed from separate feeders to a rod-forming conveyor belt as follows:
"a pocket gear draws up the milder blend by suction from the first feeder and distributes it in small piles on the conveyor belt at equal intervals. The stronger blend is then drawn from below and placed in the gaps".
This type of rod-forming operation and apparatus to effect the same is described in published U.K. patent applications Nos. 2,134,768 (= U.S. Pat. No. 4,605,013), 2,171,887 (= U.S. Pat. No. 4,693,263), 2,171,888, 2,171,889 (= U.S. Pat. No. 4,693,262) and 2,172,187 (U.S. Pat. No. 4,693,263).
With the exception of U.K. patent publication No. 2,172,187, the stronger blend tobacco is showered onto the spaced-apart discrete lengths of the milder blend tobacco on the conveyor surface and the stronger blend tobacco which overlies the discrete lengths of milder blend tobacco. In the case of U.K. patent publication No. 2,172,187, discrete lengths of the stronger blend tobacco are formed in the same way as the discrete lengths of milder blend tobacco and positioned between the discrete lengths of the milder blend tobacco on the conveyor surface. The rod forming operation described in this prior art is complex in operation and difficult to control to obtain a consistent product.
Other attempts to form multiple blend cigarette rods is described in the art. U.S. Pat. No. 3,880,171 (= W.G.O.S. 2,259,814) describes a procedure in which tobacco of a first blend is showered onto a rod-forming conveyor to form a generally uniform filler rod, which then is carried past trimming knives which cut the rod into discrete tobacco lengths of a double wedge profile. These discrete lengths of tobacco then are showered upon by another blend of tobacco to fill the gaps between and to overlie the discrete lengths. Excess tobacco then is trimmed to provide the final rod. This procedure differs from that described in the above-noted published U.K. patent application in that the discrete tobacco lengths are formed in two steps and have a double-wedge profile.
U.S. Pat. No. 4,009,722 (= W.G.O.S. 2,445,856) again is similar to the procedure of the published U.K. patent application, except that the gaps between the discrete lengths of the first blend are filled in from a downwardly-flowing shower and the discrete lengths are formed from a downwardly-flowing shower on a pocket vacuum wheel.
U.S. Pat. No. 4,630,618 is similar to U.S. Pat. No. 3,880,171 in that the discrete lengths of tobacco which are subsequently showered upon are formed from a continuous filler rod, in this instance by selective blowing tobacco from the filler rod.